Wall-type and indoor residual spraying application quality affect the residual efficacy of indoor residual spray against wild malaria vector in southwest Ethiopia

Abstract

BackgroundResidual efficacy of indoor residual spray may vary with different spray quality and wall surfaces types. This study evaluated the impact of spray quality and wall surface types on residual efficacy of propoxur against wild Anopheles gambiae sensu lato (s.l.) in southwest Ethiopia.MethodsThirty houses of different mud wall surfaces (10 smooth, 10 rough, 10 painted) were selected and randomly allocated into routine and standard spray. The routine spray was conducted by district health office as usual, while the standard spray was done by strictly following guidelines. Three control houses were selected from unsprayed nearby semi-urban. Wild An. gambiae s.l. were used for wall bioassay tests. Two-way mixed model analysis of variance was used to analyse the data. The mean variation between wall and spray types was compared by post hoc analysis of IBM SPSS version 20.ResultsOn standard spray, knockdown rate was 95.3% on painted, 82% on smooth and 72.5% on rough surface at week 17 of post-spray, whereas on routine spray it was 82.7% on painted, 48.7% on smooth and 60% on rough surface. On standard spray, mortality rate of An. gambiae s.l. was 99.3% on painted surface, 90% on smooth and 80% on rough surface. On routine spray, it was 89.3% on painted, 61.3% on smooth and 65% on rough surface at week 17 of post-spray. The painted wall surface showed the highest knockdown rate (86.4–100%) on standard and (73.8–91.5%) routine spray; mortality rate was more than 80% on both spray types during the 17 weeks of follow-up regardless of spray types. The lower mortality rate and residual effect was observed on routine smooth and rough wall surfaces. The residual efficacy of propoxur was > 80% at week 17 on standard spray regardless of the wall types and it was < 80% on routine spray except painted wall surface.ConclusionThe painted wall surface and standard spray showed better residual efficacy. Therefore, it is recommended to consider the wall surface available in the community to estimate the residual lifespan of the insecticide, and strictly to follow the spray guideline to improve the effectiveness of indoor residual spray.

Outdoor residual spray for the control of monkey malaria vectors in Sarawak, Malaysia

“…This finding is supported by Rohani et al, [4] who stated that efficacy of deltamethrin can be varied depending on the concentration used, formulation, surface of the area, humidity, temperature, and method of evaluation. Significant variation in residual efficacy between different types of wall surfaces was also reported by Desalegn et al, [10] using propoxur and Mutagahywa et al [11] using lambda-cyhalothrin who observed significant differences in mortality rate of An. gambiae exposed to different wall surface types sprayed with the same insecticide.…”

“…Briefly, the DNA was first extracted using the DNeasyR Blood & Tissue Kit (Qiagen, Valencia, CA). Mosquitoes were then undergoing the detection of malaria parasite using semi-nested and nested PCR techniques followed by sequencing analysis of the small-subunit (SSU) rRNA gene [9] .…”

Effect of wall type, delayed mortality and mosquito age on the residual efficacy of a clothianidin-based indoor residual spray formulation (SumiShield™ 50WG) in southern Mozambique

“…Residual efficacy differed slightly between type of wall surface. This has been shown for SumiShield TM 50WG and other IRS products before, but the direction of effect is not always consistent [17][18][19]. A multi-country study conducted by Oxborough and colleagues across west and east Africa assessing the residual effect of different IRS products on different wall surfaces showed that residual efficacy of each IRS product was affected by the type of surface and that variations in retention of the active ingredient can differ from country to country, even on similar surfaces [43].…”

“…As part of routine monitoring and evaluation (M&E) operations, the residual efficacy of SumiShield TM 50WG was evaluated during the 2018-2019 malaria season. Two different -but common-wall surface (cement and mudplastered) were evaluated, as type of surface is known to affect the residual efficacy of a variety of IRS products [17][18][19]. Apart from testing young (2-5 day old) mosquitoes, which is the current recommendation of WHO, older mosquitoes were exposed as well, and mortality post-exposure tracked for up to 5 days.…”

Modelling malaria reduction in a highly endemic country: Evidence from household survey, climate, and program data in Zambia

“…It may not also be efficient to spray all housing structures with residual insecticides as it has been shown to work better on painted walls compared to rough walls. 28 ITNs, on the other hand, have been shown to have little or no effect on malaria prevalence, particularly in low malaria epidemiological settings. 29 But other interventions such as MDA and community case management are effective in low endemicity settings.…”